Interpersonal problem as a common phenomenon that Chinese college students may meet in their daily life is very important for individual’s mental health (Shen, Cheng, Jin & Xi, 2011). Researches of attachment have indicated that attachment avoidance and attachment anxiety would influence individual’s interpersonal adaptation in different ways (Rholes, Simpson, Tran, Martin, & Friedman, 2007; Edelstein & Gillath, 2008). Moreover, attachment is a relatively stable character which doesn’t change in a period of time. Thus it is important to find out the mechanism of the influences of attachment on individual’s interpersonal adaptation. Self-determination theory demonstrates that autonomy need is a basic need for individual’s development. One person is autonomous when his/her behavior is experienced as willingly enacted (Ryan & Deci, 2000). A growing body of research has documented the contributing role of the satisfaction of autonomy need in interpersonal adaptation (Soenens, et al., 2007). Notably, autonomy is not the opposite of dependence. Keeping a security relationship with important others is good for the development of autonomy (Niemiec, et al., 2006; Feeney, 2007). Overall, it is reasonable to assume that individual’s autonomy could have mediating effect on the relationship between attachment and their interpersonal adaptation. To investigate the possible initial mechanism of the influences of the attachment (attachment avoidance and attachment anxiety) on individual’s interpersonal adaptation, a total of 638 college students (349 men and 289 women) from four different universities in Xi’an, Shaanxi province were assessed by questionnaires. The present study used Relationship Scale Questionnaire (Wang, Zhang, Li, & Liu, 2007) to assess the attachment character of the participants, Self Regulation Questionnaire (Liu, 2006) to assess the participants’ autonomy, and Chinese College Student Adjustment Scale (Fang, Wo, & Lin, 2005) to measure the states of the participants’ interpersonal adaptation. The data was analyzed with SPSS 15.0 and LISREL 8.7. According to the structural equation models, the results indicated as follows: (1) the predictive effects of attachment and autonomy on interpersonal adaptation are significant and effective; they can explain 57.1% of the variation of interpersonal adaptation; (2) autonomy fully mediated the relation between the attachment anxiety and individual’s interpersonal adaptation; (3) attachment avoidance contributes to interpersonal adaptation directly. Individual’s autonomy is an important mediator of the influence of attachment on interpersonal adaptation. These findings suggest that teachers and parents can improve college students’ interpersonal adaptation through meeting their autonomy needs. There is important realistic significance in finding more effective ways to improve college students’ physical and mental health.